linux-kernel - Re: [PATCH v2 04/12] tty: serial: samsung: prepare for different IO types

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Message-ID: <2024010432-taco-moneyless-53e2@gregkh>
Date: Thu, 4 Jan 2024 16:32:27 +0100
From: Greg KH <gregkh@...uxfoundation.org>
To: Tudor Ambarus <tudor.ambarus@...aro.org>
Cc: peter.griffin@...aro.org, robh+dt@...nel.org,
	krzysztof.kozlowski+dt@...aro.org, mturquette@...libre.com,
	sboyd@...nel.org, conor+dt@...nel.org, andi.shyti@...nel.org,
	alim.akhtar@...sung.com, jirislaby@...nel.org,
	s.nawrocki@...sung.com, tomasz.figa@...il.com,
	cw00.choi@...sung.com, arnd@...db.de, semen.protsenko@...aro.org,
	andre.draszik@...aro.org, saravanak@...gle.com,
	willmcvicker@...gle.com, linux-arm-kernel@...ts.infradead.org,
	linux-samsung-soc@...r.kernel.org, linux-clk@...r.kernel.org,
	devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-i2c@...r.kernel.org, linux-serial@...r.kernel.org,
	kernel-team@...roid.com
Subject: Re: [PATCH v2 04/12] tty: serial: samsung: prepare for different IO
 types

On Thu, Dec 28, 2023 at 12:57:57PM +0000, Tudor Ambarus wrote:
> GS101's Connectivity Peripheral blocks (peric0/1 blocks) which
> include the I3C and USI (I2C, SPI, UART) only allow 32-bit
> register accesses. If using 8-bit register accesses, a SError
> Interrupt is raised causing the system unusable.
> 
> Instead of specifying the reg-io-width = 4 everywhere, for each node,
> the requirement should be deduced from the compatible.
> 
> Prepare the samsung tty driver to allow IO types different than
> UPIO_MEM. ``struct uart_port::iotype`` is an unsigned char where all
> its 8 bits are exposed to uapi. We can't make NULL checks on it to
> verify if it's set, thus always set it from the driver's data.
> 
> Signed-off-by: Tudor Ambarus <tudor.ambarus@...aro.org>
> ---
> v2: new patch
> 
>  drivers/tty/serial/samsung_tty.c | 9 ++++++++-
>  1 file changed, 8 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/tty/serial/samsung_tty.c b/drivers/tty/serial/samsung_tty.c
> index 66bd6c090ace..97ce4b2424af 100644
> --- a/drivers/tty/serial/samsung_tty.c
> +++ b/drivers/tty/serial/samsung_tty.c
> @@ -72,6 +72,7 @@ struct s3c24xx_uart_info {
>  	const char		*name;
>  	enum s3c24xx_port_type	type;
>  	unsigned int		port_type;
> +	unsigned char		iotype;
>  	unsigned int		fifosize;
>  	unsigned long		rx_fifomask;
>  	unsigned long		rx_fifoshift;

Is there a reason you are trying to add unused memory spaces to this
structure for no valid reason?  I don't think you could have picked a
more incorrect place in there to add this :)

Please fix.

thanks,

greg k-h